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The longest haul

One of the key suppliers to Switzerland’s Gotthard base tunnel bills the structure as both novelty and “remarkable achievement in engineering.” At 57 meters or 35 miles, it is the world’s longest rail tunnel; passes through one of the highest Alpine massifs; and, will reduce the time that massive freight and modern high-speed trains need to travel from Zurich to Milan by around one hour.

The structure’s opening last month proved opportune for Switzerland’s top two names in concrete and cement, Sika AG and Holcim, to showcase their technology and material contributions to a mammoth undertaking. Topping Sika’s schedule for the job were 20,000 tonnes of concrete admixtures and Sikaplan membranes sealing 3.3 million square meters of bored or excavated surface area.

Between the Gotthard and companion Ceneri tunnel contracts, Holcim Switzerland will deliver 2.3 million cubic meters of ready mixed concrete and 1 million-plus tonnes of cement. Nearly 10 million of the 28.2 million tonnes of aggregates excavated for the Gotthard structure were used in the ready mixed concrete, the remaining volume placed on access routes and related infrastructure.

Holcim Switzerland commenced research to find the right concrete and shotcrete mix designs and application methods in 1996, creating a test gallery to account for characteristics of the rock to which the materials would be applied. Certain concrete mixes required lengthy set time delays—up to 12 hours—due to transport from a batch plant to point of placement. A specially developed train with mobile mixing and custom transfer units played a critical role in ensuring that concrete volumes, peaking at 2,300 cubic meters on 24-hour cycles, were delivered to spec.

PHOTOS: AlpTransit Gotthard Ltd. (post-membrane construction); Sika AG (membrane)
Sika technologies factor heavily in the Gotthard base tunnel’s waterproofing, fire protection, coating solutions. Its admixtures, coupled with Holcim cement and aggregates, yielded inordinate shotcrete and concrete expanses.